One of the biggest problems we have when we talk about training is that we tend to only talk about physical stressors.

We like complicated periodization models, manipulating training volume, intensity, and frequency. In short, we like having a sense of control. We like thinking, “If I plan out and control these training factors, I’ll get this outcome.” Sure, nutrition and sleep play a role too, but as long as those factors (often given the blanket term “recovery”) are accounted for, you’re in the clear.

However, those factors don’t paint the whole picture. Biology is messy. Your body is not a simple machine that you can feed inputs and expect predictable outputs.

Now, you can have a general idea of what’ll happen. But 1+1 doesn’t always equal 2. Maybe it’ll be 2 most of the time, but sometimes it’ll be 5, and sometimes it’ll be -3. The reason is that your body isn’t in a static state, only being challenged by the workouts you put it through. There are billions of reactions taking place in your body every moment affecting what’ll happen at the systemic level, while dozens of inputs are simultaneously entering the system via your thoughts and your senses (which then affect and modify other thoughts and sensations). 1+1 won’t always equal 2, because your body isn’t dealing with 1+1. It’s dealing with 1+1 plus a million other inputs and moderating factors. The result may be between 1.5 and 2.5 most of the time, but there’s plenty of built-in ambiguity that’s difficult to predict, harder to account for, and impossible to quantify.

Biology is nonlinear. You cannot control it. You can, at best, influence it.

Via trial and error, you can get a pretty good idea of how your body will respond to a certain set of training parameters. However, that response is still context-specific, and is largely mediated by how well your body can respond to stress. When you’re in a comfortable schedule with a 9-to-5, a predictable social life, no large sleep or diet perturbations, etc., you can develop a good idea of how your body will respond to training stress. The more constant the other inputs, the more predictable the result of imposing a particular stressor (training, in this case) will be.

However, increase the overall stress your body is coping with, and your ability to then cope with a given level of training stress is decreased. Although simplistic, Selye’s “General Adaptation Syndrome,” (pictured at the top of the article) is still very useful, even 80 years after its introduction.

Even if your training inputs haven’t changed, the rest of the inputs feeding into the system have changed, so the system with respond differently and perhaps unpredictably.

General Adaptation Syndrome essentially says that your body feeds all of its stress into a generalized pool of “adaptive reserves” that your body can use to elicit the specific adaptations necessary to respond to the stressor and strengthen the body against it in case the same stressor presents itself in the future. In the case of lifting, the strain on the structural and metabolic capabilities of the muscle are the stress, and your body responds by building larger muscles with more ability to resist strain and more of the enzymes necessary to handle exercise metabolically. However, if other stressors (work stress, poor sleep, heavy drinking, marital issues, moving to a new city, etc.) are present, they’re dipping into those adaptive reserves, so your body can’t respond as robustly to exercise.

This is something we all “know,” but which hasn’t gotten much attention in research. In fact, though specific stressors’ (sleep deprivation, food deprivation, high altitude, etc.) influence on exercise and subsequent adaptations have been studied for decades, there was actually only one measly study previously conducted on how general stress affects recovery from strength training, and it lasted less than 24 hours (i.e. not long enough to assess recovery on any meaningful scale).

The researchers sent out a questionnaire to 1,200 people to place them on the Perceived Stress Scale (PSS). Based on their PSS scores, the researchers purposefully sought out people who scored high or low on the scale to make sure there was a significant difference in stress level between the participants.

Participants

All the participants were enrolled in college weight training classes.

Once the subjects were selected, they were given two stress-related questionnaires. One was to place them on the PSS scale again (to see if their scores had changed since they last filled out the questionnaire), and one was the Undergraduate Stress Questionnaire (USQ).

PSS evaluates how stressed you *feel.* USQ evaluates how many stressful events are taking place in your life. This is a useful distinction to make, because some people tend to be able to just let the stress roll off their backs, so to speak. Others respond more negatively to life stressors. The high-stress group in this study both had stressful events in their lives, and felt mentally stressed about those things.

Procedure

The study procedure was pretty freaking brutal. The subjects worked up past a 10rm (i.e. they did sets of 10 until they could no longer complete 10 reps). Then they dropped back to their established 10rm for another set of 10. Then they took 10% off the leg press for another set of 10. If they got all 10 reps with that weight, they stayed with that weight and did 4 more sets to failure. If they didn’t get 10 reps, they took 10% more off and did 4 more sets to failure.

Before the training session, the researchers measured Maximal Isometric Force (using the same leg press – MIF), vertical jump height, and cycling power. They reassessed MIF directly after the workout and 60 minutes post-workout, and they reassessed all 3 performance-related variables at 24, 48, 72, and 96 hours post-workout.

They also assessed soreness, perceived physical energy, and perceived physical fatigue before the workout, directly after, 60 minutes after, and at 24, 48, 72, and 96 hours post-workout by having a number line with a statement like “I have no feelings of soreness” on one end and “strongest feelings of soreness ever felt” on the other end, and telling the subjects to place a mark on the line that corresponded with how sore they felt.

Results

First of all, it should be noted that there were no significant differences in any of the parameters (MIF, 1rm strength, jump height, cycling power, etc.) between groups at the start of the study. Additionally, total workload and cardiovascular response to exercise (max and average heart rate) were similar between the high stress and low stress groups, indicating that the results can’t simply be explained by saying one group worked harder than the other.

Rate of recovery from exercise was strongly correlated with the stress inventories.

For Maximal Isometric Force, everyone was gassed after the workout, with strength dropping off almost 50% directly post-workout, recovering substantially at 60 minutes post-exercise, and continuing to improve from there.

However, the low-stress group had already fully recovered by 48 hours post-exercise, whereas it took a full 96 hours for the high stress group to recover pre-exercise MIF.

It should be noted: The researchers found this pattern by simply comparing the high stress and low stress groups. Then, to make sure there weren’t confounding factors, they made adjustments for fitness, training experience, and workload and found the same pattern still held true.

Cycling power and vertical jump height were less affected by the exercise bout, and recovered much faster in both groups – near pre-exercise levels by 24 hours post-exercise. The researchers theorized that this could be explained by specificity. MIF was assessed on the same leg press used as the workout, so that was the movement pattern showing the most fatigue.

Perceptions of energy, fatigue, and soreness were also affected by stress. The higher stress group had less energy, more fatigue, and more soreness for longer than the low stress group.

Takeaways

The results of your training can’t be reduced to how many sets, reps, and exercises you did. Other factors affect how your body will respond to exercise.

Furthermore, you can’t take your exercise performance in the gym today as an indicator of how hard you SHOULD be training, given other stressors. Both groups lifted a similar amount of weight, did a similar amount of volume, and had similar cycling power and vertical jump height.

That’s one factor that makes overtraining/overreaching tricky to manage. We like looking for objective signs – getting fewer reps, being able to lift less weight, etc. However, if this study is any indication, other stressors start interfering with exercise recovery prior to performance taking a major hit.

Having a difficult time recovering from a single session may not seem like a big deal, but it adds up over time when you’re dealing with chronic stress. The same research group found that over 12 weeks of training, people with high life stress gained less strength in the squat and bench press than people with low life stress.

As was previously mentioned, the stressed-out people in this study both had stressful events taking place in their lives, AND they felt stressed about them. You can’t make any statements from this study about someone who has a lot of life stressors but who manages to stay feeling relaxed, or about someone who has fewer stressors but who still lets every little thing stress them out. My hunch is that the perception of stress matters more than the volume of stressors themselves, but this study doesn’t address that distinction. I’d love to see a follow-up study looking at people with high PSS scores, and low USQ scores (feel stressed without many stressors) and people with low PSS scores and high USQ scores (stressful life events, but minimal feelings of stress).

Interestingly, much of the research cited in this article had to do with wound healing. While the connection between muscle repair and wound healing isn’t 1 to 1, there are some notable similarities. Namely, both are mediated by the inflammation pathway to a large extent, and both are inhibited by glucocorticoid dysregulation. Psychological stress screws with cytokine signaling (including IL-6, IL-1b, and TNF-a) and results in a chronic elevation of cortisol.

In non-nerd speak, when your body’s stress response is switched “on” too much, for too long, the pathways that mediate the inflammatory response and tissue repair don’t work quite as well as they should. As a result, wounds heal slower and/or you take longer to recover from training.

Remember, you can’t just draw out a plan on paper, look at the volume, intensity, and frequency, and know how your body will respond to it 100%. What may be low volume and easy to recover from in a situation with minimal life stress may be high volume and crushingly difficult when other stressors in your life rear their heads. Ongoing adjustments need to be made, and some wiggle-room needs to be built in so you can alter your training stress based on what life throws at you.

This isn’t to say there’s no value in having a plan. It just means that plan needs to be interpreted more like a compass than like a road map.

Of course, ambiguity stresses some people out more than others. I love things that have a lot of gray area, while other people hate them, and want everything spelled out. In that case, a training plan with too much wiggle room can, paradoxically, cause more of the psychological stress that it was intended to moderate and account for. I think that’s one reason RPE-based training works so well for some people (people who can handle more gray area) but not-so-well for others (people who agonize about whether something was REALLY an 8RPE or not).

You are a psychosomatic being.

Psycho = mind

Soma = body

You can’t divorce the two. Mental stress can manifest itself as physical stress, and physical stress can manifest itself as mental stress.

Don’t be fooled into thinking the only thing that matters when it comes to training are the sets and reps you do in the gym.

Don’t be fooled into thinking the time between training sessions, the food you eat, and the sleep you get are the only things that matter when you talk about recovery. Those things matter, but so do the other events in your life, and your perceptions about those events.

Conceptually, you should think of your body not as a machine, but rather as a garden. With a machine, as long as it has a power supply and none of its parts are faulty, you can feed in certain inputs and expect predictable outputs. When you think about your body as a machine, you tend to focus excessively on just the training side of the equation. “I’m alive (power source). I’m not injured (all the parts are functional). If I follow this training program or make this training adjustment, then I’m bound to get these results.”

Sometimes that works. But, more often that not, it results in failure and frustration.

When you think about your body as a garden, it’s almost ludicrous to even consider the idea of forcing some type of adaptation. All you can do is nurture it and provide it with the best conditions for growth. You fertilize it, tend the soil, uproot the weeds, water it, leave it in the sunlight, and give it the best conditions for growth. It will only grow as well as its circumstances allow.

That’s a much more accurate metaphor for how training works. A holistic view of training treats sleep, nutrition, stress management, and enjoyment and motivation as conditions just as necessary for growth as the actual training itself. This is something we stress in The Art and Science of Lifting, because most people have solid training plans (there are enough solid options on the Internet to choose from, that people rarely do anything TOO backward, training-wise) but still fail to get the results they expect. Knowing what out-of-the gym factors make the biggest difference, and knowing how to address them makes a tremendous difference.

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About Greg Nuckols

Greg Nuckols has over a decade of experience under the bar, a BS in Exercise and Sports Science, and a Master's in Exercise Physiology. He’s held 3 all-time world records in powerlifting in the 220 and 242 classes.

He’s trained hundreds of athletes and regular folks, both online and in-person. He’s written for many of the major magazines and websites in the fitness industry, including Men’s Health, Men’s Fitness, Muscle & Fitness, Bodybuilding.com, T-Nation, and Schwarzenegger.com. Furthermore, he’s had the opportunity to work with and learn from numerous record holders, champion athletes, and collegiate and professional strength and conditioning coaches through his previous job as Chief Content Director for Juggernaut Training Systems and current full-time work here on Stronger By Science.

His passions are making complex information easily understandable for athletes, coaches, and fitness enthusiasts, helping people reach their strength and fitness goals, and drinking great beer.